1. Field of the Invention
The present invention relates to an eleotrophotographic photosensitive member which comprises a photosensitive layer containing a specified charge-generating substance, and a resin having a specified structure. The present invention also relates to an electrophotographic apparatus, a device unit, and a facsimile machine, employing the electrophotographic photosensitive member.
2. Related Background Art
Known organic photoconductive substances useful for electrophotographic photosensitive members include photoconductive polymers such as poly-N-vinylcarbazole, and low-molecular organic photoconductive substances such as oxadiazoles and azo pigments. Electrophotographic photosensitive members employing an organic photoconductive substance have advantages of non-pollution, very high productivity, relative inexpensiveness, and so forth. The sensitivity range of the photosensitive members can be relatively readily controlled by selection of the substance employed. Accordingly, use of the organic photoconductive substances have been comprehensively studied for electrophotographic members. Conventional organic electrophotographic photosensitive members were considered to be defective in sensitivity and durability. However, in recent years, the sensitivity and the durability thereof have been remarkably improved as the result of the development of function-separation type photosensitive members which are constituted of a charge-generating layer containing a charge generating substance laminated to a charge-transporting layer containing a charge-transporting substance.
On the other hand, non-impact type printers which utilize the electrophotography technique have come to be widely used as a terminal printer in place of conventional impact type printers. Most of such non-impact type printers are laser beam printers employing a laser light as the irradiation light source. In most cases, semiconductor lasers are used for the laser light source in view of the cost and the size of the apparatus. The semiconductor laser emits light of wavelength as long as 790.+-.20 nm. Therefore, electrophotographic photosensitive members are now being investigated which have sufficient sensitivity to light of such a long wavelength.
Phthalocyanine compounds are extremely effective as the charge-generating substance sensitive to light of such long wavelengths. In particular, oxytitanium phthalocyanine has excellent sensitivity characteristics in comparison with usual. phthalocyanine compounds. Various crystal forms of highly sensitive oxytitanium phthalocyanine are disclosed in literature such as Japanese Patent Application Laid-Open Nos. 61-239248, and 61-217050, Japanese Patent Publication No. 62-67094, Japanese Patent Application Laid-Open Nos. 63-218768, and 64-17066.
However, electrophotographic photosensitive members employing oxytitanium phthalocyanine, which have excellent sensitivity characteristics, are liable to cause charge injection from the support at a high temperature and a high humidity. Particularly when used in a reversal development type of electrophotographic apparatus, this type of photosensitive member is liable to cause spot-shaped fogging (hereinafter referred to as "black spots") in non-printed areas of a printed image. Further, the photosensitive member is liable to cause variation of a light area potential on repeated use.
To meet the demand for high quality of images and durability of the members in recent years, electrophotographic photosensitive members were investigated which are capable of providing high-quality images stably.